Forming catch tabs on paperboard food container components for retaining containers and lids in releasable attachment

ABSTRACT

A die set apparatus for forming catch tabs on a flange of a first paperboard container component, such as a lid, while the paperboard is being pressed between a pair of mating dies. A plurality of cavities are formed in and circumferentially spaced around a first die, each cavity opening toward a second die and having a shearing edge. A plurality of radial passages extend through a second die, each passage in registration with one of the cavities. A plurality of catch punches are mounted for radial movement through a radial passage and into its associated cavity. Each catch punch also has a shearing edge aligned to closely slide past the shearing edge of its associated cavity. An actuator drives the catch punches into the cavities to shear a slit in the interposed paperboard and drive an adjacent segment of paperboard into the cavity to preform the catch tabs. As the dies are separated, each catch tab is caught on the edge of the cavity and bent inwardly, tearing the paperboard at opposite ends of the slit so that the tears form opposite sides of the catch tabs.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the manufacture of catch tabs onpressformed, paperboard, food container component parts, such as lidsand trays, for retaining food container components in manuallyreleasable attachment.

2. Description of the Related Art

A popular type of package for food and beverages is a two-part packageconsisting of a lower container and a cover which have mating rims thatpermit the two to be removably attached together in order to enclose thefood. They have mating rims that are typically characterized by aperipheral, annular lip, such as a rolled rim or a generally horizontalflange, on one of the two parts and a peripheral, generally axiallyextending, annular flange on the other part that has projecting catchtabs that can be passed over and then latched against the lip or flange.Usually, the generally axially extending, peripheral flange extendsoutwardly of and surrounds the lip or generally horizontal flange andthe catch tabs extend radially inwardly from the axially extendingflange. However, these relative positions can be reversed.

Food containers of this type come in a variety of configurations havingother common features. Usually, one part of the container has sidewallsof substantial height and the other part is relatively flat, with nosubstantial sidewalls. For example, for beverages, such as soft drinksand coffee, the lower part has sidewalls of a substantial height with anoutwardly extended rolled lip around its top rim and receives andsupports the food item. The upper part is a relatively flat lid forcompleting the enclosure and is formed by a panel with a peripheral,axially extending flange with radially inwardly extending catch tabs.For some food products, such as cakes or vegetables, these relativepositions are reversed so that the lower part is relatively flat, itreceives and supports the food item and is referred to as a tray or dishand the upper part has sidewalls of a substantial height for completingthe enclosure of the food item and is sometimes referred to as a cover.For still other food items, both component parts have sidewalls ofsubstantial height. All of these types of container structures can beinverted and their size can be modified and they still are containershaving a lower component part and an upper component part.

Furthermore, the lip or flange can be formed on either the upper or thelower component part and the generally axially extending, annularflange, with its catch tabs, can be formed on the other component part.Therefore, terms such as lid, tray, cup, dish etc. can be misleading andconfining when used with these containers because those terms imply atop or bottom position even though the structural features areinterchangeable.

In view of this variability and the interchangeability of the position,size and orientation of these container structures, and in an attempt tohave a consistent terminology without requiring multiple repetitions ofsubstantial equivalents, certain terminology has been adopted. Insteadof the terms lid, cup, tray, dish, etc. the term “container componentpart” is used and containers to which the invention applies ordinarilyhas two container component parts. The term “axially extending flange”is used to refer to the structure on a first component part of acontainer that has catch tabs for releasably latching the firstcomponent part to the second component part. When the components arejoined, the axially extending flange is usually located outwardly of andsurrounding the lip or flange of the second component part. The term“lip” is used to refer to the lip or flange of the second component partthat is held by the catch tabs. It should be understood, however, thatthe term “axially extending flange” is not confined to a flange-likestructure that is itself necessarily parallel to the axis of thecontainer component part. That flange is usually somewhat oblique to theaxis. It is only necessary that the “axially extending flange” liegenerally along a resultant that has a directional component that isparallel to the axis so that, when the container component parts aremoved along their axes to bring the two component parts into closedengagement, the catch tabs will pass over and then latch to the lip.

Additionally, while some container component parts have substantialsidewall heights and some do not, all can be described as having an“open end” and a “closed end”. The open end is the axial end of acontainer component part that faces the other component part and the twocomponents are joined at their open ends. For example, a lid has a panelextending across and closing its top and a cup and a tray each have abottom panel closing its bottom. Both the axially extending flangeformed with the catch tabs and the lip that engages the catch tabs aretypically formed near the open ends of the container component parts.The axially extending flange can extend from and be integrally formedwith a wall of a peripheral groove formed in a closed panel of a lid orplate. The axially extending flange can extend from a sidewall and itcan be an integral extension of a sidewall.

Thermoformed drinking cup lids, cake platforms, and other various typesof carry-out food packaging made from several types of plastic materialshave long been used in the food and beverage industry. Plastic materialsare easily molded or formed into desired shapes. Consequently, plasticfood container component parts have long been formed with catch tabs orindentations protruding from an axially extending flange on a firstcontainer component part to latch the first component part onto a secondcomponent part. This is most common for lids for soft drinks and coffee.

Paperboard has also long been used for forming component parts for foodcontainers. One successful manufacturing technique is pressforming orthermoforming of the paperboard. In this technique, paperboard stock,typically corrugated paperboard, is pressed between mating, heated diesand formed into a desired shape. The pressforming of paperboard has beenused to form a broad variety of container component parts.

Many consumers and companies would prefer to use paperboard for lids,trays and other container component parts because paperboard has betterinherent insulating properties and better graphic printing capabilities,is more environmentally friendly because it more readily and quicklydeteriorates when discarded outdoors and is a renewable resource.However, in the past it has not been possible to obtain tight fittinglids or other container component parts in certain applications with theuse of paperboard and/or combinations of paperboard and plastic. Thishas been primarily due to the fact that it has not been possible to forminterior or “reversed” catch tabs in the paperboard packaging using theconventional male/female forming dies utilized in the existingpressforming technology.

It is therefore an object and feature of the invention to provide amethod and apparatus that can be used to form catch tabs on the axiallyextending flange of a container component part for latching with the lipof another container component part and to provide a paperboardcontainer component part having such catch tabs.

BRIEF SUMMARY OF THE INVENTION

Catch tabs are formed on an axially extending flange of a firstpaperboard container component part by shearing a plurality ofcircumferentially spaced slits through the axially extending flange andradially punching the paperboard adjacent each slit to deform a segmentof the paperboard adjacent the slit in a radial direction. Preferably,each catch tab is caught on an edge formed on one of the forming dies,as the dies are separated, so that the catch tab is bent away from theaxially extending flange and toward the open end of the containercomponent part. This bending tears the paperboard at opposite ends ofthe slit so that the tears form opposite sides of the catch tab.

To do this, a plurality of cavities are circumferentially spaced arounda first die portion, each cavity opening toward a second die portion andhaving a shearing edge. A plurality of radial passages extend throughthe second die portion, each passage in registration with one of saidcavities. A plurality of catch punches are each mounted for radialmovement through a radial passage and into an associated one of thecavities. Each catch punch includes a shearing edge aligned to closelyslide past the shearing edge of its associated cavity. An actuator isdrivingly linked to each catch punch for driving the catch punches intothe cavities and thereby shearing a slit in the interposed paperboardand driving an adjacent segment of paperboard into the cavity to formthe catch tab or an initial preform of the catch tab.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIGS. 1-3 are half views in axial section of paperboard forming diesincorporating an embodiment of the invention and illustrating itsoperation.

FIG. 4 is a view in frontal perspective of the preferred embodiment ofthe invention.

FIG. 5 is a view in perspective of the upper die of the embodiment ofFIG. 4.

FIG. 6 is a view in perspective of a portion of a lower die of theembodiment of FIG. 4 with an assembled actuator, catch punch and asupport bracket removed from the lower die to reveal its structure.

FIG. 7 is a view in perspective looking the opposite direction at thestructures illustrated in FIG. 6.

FIG. 8 is a view in side elevation of a segment of the die of FIG. 6with the catch punch, support bracket and actuator removed to reveal thepassage through which the catch punch extends and retracts.

FIG. 9 is a view in perspective showing in greater detail a portion ofthe upper die illustrated in FIG. 4.

FIGS. 10-12 are vertical sectional views of the dies of the embodimentof FIG. 4 closed upon a paperboard sheet and showing the actuator, catchpunch and cavity at sequential stages of operation.

FIGS. 13 and 14 are views in axial section like those of FIGS. 10-12 butenlarged to reveal more detail of segments of the structure illustratedin FIGS. 10-12.

FIG. 15 is a view in perspective of a container component part embodyingthe invention but shown upside down.

FIG. 16 is a view in perspective of a segment of the container componentpart of FIG. 15 shown right side up in the orientation for its normaluse as a cake plate.

In describing the preferred embodiment of the invention which isillustrated in the drawings, specific terminology will be resorted tofor the sake of clarity. However, it is not intended that the inventionbe limited to the specific term so selected and it is to be understoodthat each specific term includes all technical equivalents which operatein a similar manner to accomplish a similar purpose.

DETAILED DESCRIPTION OF THE INVENTION

The present invention utilizes standard pressforming or thermoformingdies as is well known in the art of thermoforming or pressforming ofpaperboard materials. The dies consist primarily of a heated femalecavity die, heated male punch die and may also include a heated drawring and/or an ironing ring but the dies are modified in accordance withthe invention. A blank of paperboard material is precut from a roll orsheet of paperboard and is inserted between the male and female dies asin existing technology. The paperboard material is bent and at placessmall folds are made to conform the paperboard to the forming surfacesof the dies.

FIGS. 1-3 show a relatively simple embodiment of the inventionillustrating the principles of its operation and FIGS. 4-14 show thepreferred embodiment of the invention. Referring to FIGS. 1-3, only halfof the dies and the paperboard blank are illustrated because the otherhalf is a contiguous, mirror image. A male die 10 is shown engaged witha female die 12 with an interposed paperboard sheet 14 pressed betweenthe dies and with a draw ring 15 also pressing a peripheral flangeportion of the paperboard sheet 14 against the female die 12. Thepaperboard sheet 14 is formed by the dies into a first paperboardcontainer component part that has a closing or end panel 18, an axiallyextending flange 20 and an open end that is facing downwardly in FIGS.1-3. The interior of the axially extending flange 20 is formed by a malewall die portion 22 of the male die 10 and the exterior of the axiallyextending flange 20 is formed by a female wall die portion 24 of thefemale die 12 radially outwardly from the male portion 22.

In order to form catch tabs on the axially extending flange 20,cooperating structures are provided to accomplish a secondary andgenerally radially acting punching operation while the paperboard sheet14 is held between the dies 10 and 12. In the embodiment of FIGS. 1-3, aperipheral groove 26 encircles the male die portion 22. A peripheralgroove is easier to machine into the die portion but, instead, aplurality of individual cavities can be circumferentially spaced aroundand formed in the male die portion 22 preferably at regular angularintervals, such as every 45° or every 90° for example. In effect, aperipheral groove forms a unitary series of groove segments, eachsegment being a cavity. Each cavity opens toward the oppositely facingfemale die portion 24 of the female die 12. The groove 26, and thereforeeach segmental cavity, has a shearing edge 28 formed at the edge of itsupper surface in FIGS. 1-3.

A plurality of radial passages, only radial passage 30 being visible inFIGS. 1-3, extend through the female die portion 24 with each passagealigned in registration with one of said cavities. A plurality of catchpunches, only catch punch 32 being visible in FIGS. 1-3, are mounted forradial movement through a radial passage and into an associated one ofthe cavities. For example, catch punch 32 is radially slidable throughradial passage 30 into cavity 26. Each catch punch includes a shearingedge, only shearing edge 34 being visible in FIGS. 1-3. The shearingedge 34 of the catch punch 32, like the shearing edges of all the catchpunches, is aligned to closely slide past the shearing edge 28 of itsassociated cavity in the manner of a pair of shears.

An actuator, only actuator 36 being visible in FIGS. 1-3, is drivinglylinked to each catch punch for driving the catch punches through theradial passages and into the cavities and then retracting the catchpunches while the dies 10 and 12 are engaged against the paperboard 18.The shearing edges shear a slit in the interposed paperboard and alsodrive a segment of paperboard that is adjacent the slit into the cavityto form the catch tab or a preform of it. Preferably, the ends of thecatch punches are beveled and the shearing edge of each catch punch isformed on the most distally protruding end of each catch punch to form aknife edge. In the preferred embodiments, the slit is aligned in acircumferential direction of the container component part formed by thepaperboard sheet 18. Also, in the preferred embodiments, the catchpunches, like the catch punch 32, deforms the paperboard by bending thepaperboard to form the catch tab 38 on the side of the slit that isnearer the open end of the container component part being formed. Thatcauses the catch tab 38 to be inclined toward the closed end so that,when two container component parts are engaged together, the catch tabwill more firmly resist separation of the two component parts. However,the relative positions of the slit and the catch tab can be reversed.

In operation, the dies 10 and 12, along with the draw ring 15 arepressed against opposite sides of the paperboard sheet 18 as illustratedin FIG. 1. The draw ring can be considered a die because it also pressesagainst the paperboard sheet 18 and can have contoured surfaces toreshape the paperboard sheet. The catch punch 32 is then driven throughthe passage 30 and into the cavity 26, as illustrated in FIG. 2, to slitthe paperboard and bend a small segment of the paperboard inwardly toform the catch tab 38. The catch punch 32 is then retracted out of thecavity and preferably back to its initial position. The dies then beginseparation which, for the embodiment illustrated in FIG. 3, is done bylowering the male punch or die 10. As it lowers, the upper shearing edge28 of the cavity 26 catches the catch tab 38 and bends it, as shown inFIG. 3, further inwardly, downwardly and toward the open end of thecontainer component part being formed. Although shearing edges can alsobe formed on the lateral sides of the cavity and cooperating shearingedges formed on the lateral sides of the catch punch, that is notnecessary. When the edge of the cavity catches on the catch tab andbends it inwardly, this bending of the catch tab will cause a tearing ofthe paperboard at the opposite ends of the slit. These tears define andform the laterally opposite sides of the catch tab.

Preferably, the forming surface of the die portion into which eachcavity is formed is an inclined surface as illustrated in FIG. 1-3 thatis inclined or oblique to the central axis of the dies. For forminginwardly bent catch tabs with radially inwardly actuated catch punches,the surface is inclined toward the axial center of the dies as thesurface approaches the opposite mating die. The shearing edge of thecavity is formed on the cavity edge nearest the mating die but ispreferably spaced radially inwardly from the opposite edge of the cavityby a distance that is less than the distance of protrusion of the catchtabs. That spacing assures that, upon separation of the die portions,the shearing edge of the cavity will catch so it can bend the catch tabstoward the open end of the container component part. Inclining thesurface also helps assure that the shearing edge of the cavity will notshear off the tab at its bend as the dies separate. The amount of theincline also controls the distance that the tab is bent back as the diesseparate. Paperboard has substantial resilience and therefore a catchtab that bends even beyond a 90° bend will, for most paperboardmaterials, return to extend toward the closed end of the containercomponent part.

Several variations and modifications may additionally be made. The catchpunch does not need to go all the way into the cavities. It must only gofar enough to shear the slit into the paperboard and bend the tabinwardly, preferably far enough so that the tab will catch on the cavityedge as the dies separate. If an embodiment is designed so that thepunch entirely enters the cavity, the punch needs to be thinner in theaxial direction than the cavity in that direction to avoid shearing thecatch tab at two opposite edges.

If the invention is applied to form outwardly bent tabs, the cavity,passage and punch positions and the incline would be reversed.

It is not necessary that the movement of the catch punches, andtherefore the alignment of the cavities and the passage through whichthe punch travels, always be in a perfectly radial direction. Forexample, the catch punches can travel a path that is inclined to thehorizontal plane so their travel paths are oblique instead ofperpendicular to the axes of the dies. The travel paths can lie along acone having its axis coaxial with the axis of the dies. It is onlynecessary that the travel path of the catch punches have a radialcomponent.

The cavities into which the catch punches extend to form the slit andbend the catch tab are not necessarily bounded on all sides. All that isnecessary is a shoulder to form a shearing edge. Consequently, insteadof the two sided groove illustrated in FIGS. 1-3, the groove couldextend (downwardly in the figures) all the way to the paperboard andthereby form only a shoulder at which the shearing edge is formed. Itwill be apparent to those skilled in the art that this has thedisadvantage of reducing the forming surface area of the die. However,for some container component part configurations, the lost formingsurface may not be necessary.

A unique aspect of this invention is that it provides a system ofextending/retracting punches or knives in the sidewall of a die that mayinclude a draw ring or ironing ring. One of these is provided for eachindividual catch tab. These could range in number from two to severaldepending upon the size of the container and lid and there can beupwards of 30 or 40 of these catch tabs. These punches are timed toextend via actuators, such as air cylinders, using a PLC control and asolenoid valve when the die has been closed on the paperboard.

A second unique aspect of this invention is the cavity that is cut intothe sidewall of the die forming half which is placed precisely to acceptthe extending punch with little or no clearance, thereby allowing thepunch to penetrate the paperboard material which is sandwiched betweenthe punch and the cavity. This action in and of itself does notnecessarily entirely form the catch tab, but at least slits thepaperboard and indents it slightly toward the inside of the cavity. Asthe die opens and the formed paperboard part begins to eject off of themale die, these protruding slits get “caught” on the sharp lip of thecavity, bending them away as the part continues to lift off the die,thereby forming catch tabs that can be used to hold a mating containercomponent part tightly to itself.

FIGS. 4-9 illustrate the preferred embodiment of the invention.Referring to FIG. 4, a pair of dies 40 and 42 are mounted to a die presshaving a base 44 and an upper die support 46 mounted to vertical columns48. At least the upper or lower dies are vertically movable along theaxis of the dies 40 and 42 to bring the dies into engagement in theconventional manner. The axis for the preferred embodiment is a verticalaxis of symmetry for the dies 40 and 42. The upper die 40 is alsoillustrated FIG. 5 and consists of a cavity insert 50 and an ironingring 52 which are independently movable toward the lower die 42. Thelower die 42 consists of a punch 54 and a draw ring 56 which are alsoindependently movable.

FIGS. 6-8 and 9-11 illustrate more details of the lower die 42. Thepunch 54 has a convex, dished shape with an outer, convex, roundedshoulder 60. The draw ring 56 closely surrounds the punch 54 and has aninterior, concave, rounded shoulder 62. As shown in FIG. 4, eightactuators 64, preferably pneumatic actuators, are mounted to the drawring 56 at 45° angular intervals. They are operated by air underpressure supplied through air hoses 65 (FIG. 4). Each actuator 64 isfixed to a mounting bracket 66 that in turn is mounted by two cap screwsto the draw ring 56. A catch punch 68 is slidably mounted within eachmounting bracket 66 and is drivingly linked to an actuator 64 forextending and retracting the catch punch 68. Eight radial passages 70are formed through the draw ring 56 in alignment with the catch punches68 and are sufficiently large to permit the beveled, innermost ends ofthe catch punches 68 to pass through the draw ring 56.

Referring to FIGS. 9-14, the cavity insert 50 has a dish shaped formingsurface with a peripheral, rounded ridge 71. The outer surface 73 of theperipheral ridge 71 is inclined to the axis of the dies 40 and 42 andhas eight cavities 72 formed to extend into the peripheral ridge 71.This outer, inclined surface 73 together with the concave shoulder 62 onthe draw ring 56 form the axially extending flange 78 on the paperboardcontainer component part 80 into which the catch punches 68 are drivento form the catch tabs 82. Each cavity 72 is associated with a passageand a catch punch and is positioned to come into registration with apassage 72 and receive a catch punch 68 when extended by its associatedactuator 64. Each cavity also is formed with a shearing edge 74 thatcooperates with a shearing edge 76 on each catch punch to cut acircumferentially aligned slit in the paperboard sheet.

The embodiment of FIGS. 4-14 was used to construct the paperboard cakeplate illustrated in FIGS. 15 and 16. The cake plate has a peripheralgroove 84 formed by a double bend and includes an outer, axiallyextending flange 78 through which inwardly extending catch tabs 82 wereformed. These catch tabs 82 latch over the peripheral flange thatextends outwardly from a conventional, disposable cake cover (notillustrated). These catch tabs 82 were formed in the manner illustratedin FIGS. 10-14. The paperboard sheet 80 was compressed between the dies40 and 42 in the conventional manner while the catch punch was in itsretracted position illustrated in FIG. 10. With the dies 40 and 42 heldstationary, the catch punch 68 was driven by the actuator 64 along thepassage 70 and into the cavity 72. As with the embodiment of FIGS. 1-3,the shearing edges of the cavity 72 and the catch punch 68 shear thepaperboard sheet 80 to form a slit and drive a segment of the paperboard80 into the cavity 72. The actuator 64, or a spring, then retracts thecatch punch 68 and leaves the catch tab 82 protruding into the cavity 72as illustrated in FIG. 12 and the enlarged segment of it illustrated inFIG. 13. The cavity insert 50 is then raised while the ironing ring 52holds the paperboard 80 against the punch 54 and draw ring 56 of thelower die 42. As it raises, the lower shearing edge 74 of the cavity 72lifts the segment of paperboard next to the slit, tearing it at oppositeends of the slit to form the catch tab 82.

The terms male die, female die, punch and cavity insert are used todescribe the forming dies with mating surfaces that engage an interposedsheet for bending contours into the sheet. However, a die can havemultiple components each with some forming function. For example, in theembodiment described above, the lower die consists of a die punch and adraw ring and the upper die consists of a die cavity and an ironingring. The term die is used herein to refer any of the structures thathave forming surfaces whether there are one or multiple components.

Those skilled in the art will also recognize that the locations of theupper and lower dies can be interchanged and that the catch punchstructures can be mounted on either the upper or lower dies. Similarly,either one or more of the upper die components can be lowered to engagethe lower die components and raised to separate from them or one or moreof the lower die components can be raised to engage the upper diecomponents and lowered to separate. Both upper and lower die componentscould be moved toward the other but this would ordinarily requireunnecessary extra equipment. The invention can be practiced with allthese variations.

Furthermore, a die can have both male and female forming surfaces on thesame die. For example, a circular double bend can be formed at theperipheral edge of a paperboard sheet as described above. The doublebend appears on one side of a paperboard sheet as a trough encircling acentral panel and on the other side of the sheet as a circular wavehaving an inner side, an outer side and a crest rising above the centralpanel. Each die for forming such a double bend has a portion thatprotrudes into the other die and therefore the descriptive terms maleand female are not clearly applicable. When one or both dies are made ofmultiple components, one component may be male and one female on thesame die. Therefore, the term “die portion” is used, without beingdesignated male or female, to refer to a portion of a die that includesa forming surface.

The term “radial” is not intended to be limited to the radials ofcircular container component parts. Container component parts are oftenoval or rectangular with rounded edges. Therefore the term “radial” isintended to refer to a direction generally transverse or normal to theflanges, sidewalls or lips of the container component parts.

The cavities that receive the catch punches to form the catch tabs andthe catch punches have been described as having a shearing edge. It isnot essential that the shear edges be linear. For example, the shearedges of both the catch punch and the cavity can be matingly curved orarcuate, mating sawtooth configurations or other shapes. They can alsobe aligned somewhat transverse to a plane that is perpendicular to theaxes of dies.

It is also not necessary that the cavities be located inwardly of thepassages in which the catch punches slide in order to bend the catchtabs to extend inwardly. That configuration is preferred because thereis more space outwardly of the dies for positioning of the catch punchesand their actuators and because inwardly extending catch tabs are morecommonly used. However, the cavities can be formed in the outer dieportion with the passages and catch punches inwardly of the cavities sothat the catch tabs can be bent outwardly. To do this, it would bedesirable to use linkages connecting one or more actuators to the catchpunches so the actuators can be positioned where there is adequatespace.

While certain preferred embodiments of the present invention have beendisclosed in detail, it is to be understood that various modificationsmay be adopted without departing from the spirit of the invention orscope of the following claims.

1. A method for forming catch tabs on an axially extending flange of afirst paperboard container component part during the pressforming of thefirst container component between a pair of mating dies, the containercomponent part having a closed end and an open end for engaging a secondcontainer component part, the method comprising: (a) shearing aplurality of circumferentially spaced slits through the axiallyextending flange; and (b) radially punching the paperboard adjacent eachslit to deform a segment of the paperboard adjacent the slit in a radialdirection to form the catch tabs.
 2. A method in accordance with claim 1and further comprising shearing the spaced slits along a circumferentialdirection and punching and radially deforming the paperboard on the openend side of the slit.
 3. A method in accordance with claim 2 wherein theshearing and punching operations are performed in a single operation bydriving a shearing punch member radially through openings in said dies.4. A method in accordance with claim 3 wherein the shearing punch memberis driven in a radially inwardly direction to perform the punching andshearing operation and then withdrawn.
 5. A method in accordance withclaim 1 or 2 or 3 or 4 and further comprising catching each catch tab onan edge formed on one of the dies as the dies are separated and bendingthe catch tab toward the open end of the container component part.
 6. Amethod in accordance with claim 5 and further comprising tearing thepaperboard at opposite ends of the slit during the bending step so thattears form opposite sides of the catch tab.
 7. A paperboard containercomponent having catch tabs made in accordance with the method of claim1 or 2 or 3 or 4
 8. A die set apparatus for forming catch tabs on anaxially extending flange of a first paperboard container component parthaving an open end for engaging a second container component part, thecatch tabs being formed while a sheet of paperboard is being pressed toform the first container component between a pair of mating dies, themating dies including a male die portion for pressforming the interiorsurface of the axially extending flange and a female portion forpressforming the exterior surface of the axially extending flangeradially outwardly from the male portion, the apparatus comprising: (a)a plurality of cavities circumferentially spaced around a first one ofsaid die portions, each cavity opening toward the second of said dieportions and having a shearing edge; (b) a plurality of radial passagesextending through the second of said die portions, each passage inregistration with one of said cavities; (c) a plurality of catchpunches, each punch mounted for radial movement through a radial passageand into an associated one of the cavities, each catch punch including ashearing edge aligned to closely slide past the shearing edge of itsassociated cavity; and (d) an actuator drivingly linked to each catchpunch for driving the catch punches into the cavities and therebyshearing a slit in the interposed paperboard and driving an adjacentsegment of paperboard into the cavity to form the catch tab.
 9. Anapparatus in accordance with claim 8 wherein the shearing edges of thecatch punch and the cavity are positioned on the respective edges ofboth each catch punch and each cavity that are closer to the closed endof the container component part.
 10. An apparatus in accordance withclaim 9 wherein a cavity entering end of each catch punch has a beveledend and a distally protruding edge of the beveled end forms a knife edgeas the shearing edge of the punch.
 11. An apparatus in accordance withclaim 8 or 9 or 10 wherein the first portion having the cavities isinward of the second portion having the radial passages and wherein thecatch punches are retractable outwardly where they are disengaged fromthe cavities and are extendible radially inwardly into the cavities toform the catch tabs.
 12. An apparatus in accordance with claim 8 or 9 or10 wherein the cavities are formed by segments of a continuous grooveextending around the first die portion.
 13. An apparatus in accordancewith claim 8 or 9 or 10 wherein each cavity is formed into an inclinedsurface of the first die portion, the inclined surface being inclinedtoward the axial center of the dies as the inclined surface approachesthe mating die, the shearing edge of the cavity being formed on thecavity edge nearest the mating die but spaced radially inwardly from anopposite edge of the cavity less than the distance of protrusion of thecatch tabs so that, upon separation of the die portions, the shearingedge of the cavity will catch and bend the catch tabs toward the openend of the container component part.
 14. An apparatus in accordance withclaim 8 or 9 or 10 wherein each cavity has a bending edge axiallyopposite the shearing edge and wherein the catch punch has an axialthickness that is less than the axial distance from the shearing edge ofthe cavity to the bending edge of the cavity to avoid shearing thepaperboard at both edges.
 15. An improved container component parthaving at least one axially extending flange with catch tabs protrudingfrom the flange, wherein the improvement comprises: the containercomponent part being formed of a unitary sheet of pressformedpaperboard.